Secondary battery, battery pack, electric vehicle, electric power storage system, electric power tool, and electronic apparatus

ABSTRACT

A secondary battery is provided. The secondary battery includes a cathode; an anode; and a gel electrolyte, wherein the gel electrolyte includes an electrolytic solution and a polymer, and the electrolytic solution includes an unsaturated cyclic ester carbonate represented by Formula (2): 
     
       
         
         
             
             
         
       
     
     where R5 and R6 are one of a hydrogen group, a halogen group, a monovalent hydrocarbon group, a monovalent halogenated hydrocarbon group, a monovalent oxygen-containing hydrocarbon group, and a monovalent halogenated oxygen-containing hydrocarbon group; and where R5 and R6 may be bonded to each other.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.13/711,317, filed Dec. 11, 2012, which claims priority to JapaneseApplication No. 2011-280185, filed Dec. 21, 2011, the disclosures ofwhich are hereby incorporated by reference.

BACKGROUND

The present application relates to a secondary battery that includes agel electrolyte, to a battery pack, an electric vehicle, an electricpower storage system, an electric power tool, and an electronicapparatus that use the secondary battery.

In recent years, various electronic apparatuses such as a mobile phoneand a personal digital assistant (PDA) have been widely used, and it hasbeen strongly demanded to further reduce the size and the weight of theelectronic apparatuses and to achieve their long life. Accordingly, asan electric power source for the electronic apparatuses, a battery, inparticular, a small and light-weight secondary battery capable ofproviding high energy density has been developed. In these days, it hasbeen considered to apply such a secondary battery to various otherapplications represented by a battery pack attachably and detachablymounted on the electronic apparatuses or the like, an electric vehiclesuch as an electric automobile, an electric power storage system such asa home electric power server, or an electric power tool such as anelectric drill.

As the secondary battery, secondary batteries that obtain a batterycapacity by utilizing various charge and discharge principles have beenproposed. Specially, a secondary battery utilizing insertion andextraction of an electrode reactant is considered promising, since sucha secondary battery provides higher energy density than lead batteries,nickel cadmium batteries, and the like.

The secondary battery includes a cathode, an anode, and an electrolyticsolution. The electrolytic solution contains a solvent and anelectrolyte salt. The electrolytic solution functioning as a medium fora charge and discharge reaction largely affects performance of thesecondary battery. Therefore, various studies have been made on thecomposition of the electrolytic solution. Specifically, to suppressbattery degradation at the time of high-voltage charging, explosionhazard due to pressure increase inside a battery, and/or the like, acyclic ester carbonate having one or more carbon-carbon unsaturatedbonds is used as an additive of an electrolytic solution (for example,see Japanese Unexamined Patent Application Publication Nos. 2006-114388,2001-135351, H11-191319, 2000-058122, and 2008-010414; and JapaneseUnexamined Patent Application Publication (Translation of PCTApplication) No. 2004-523073). This kind of cyclic ester carbonate isused not only for a battery system using an electrolytic solution(liquid battery), but also for a battery system not using anelectrolytic solution (solid battery) (for example, see JapaneseUnexamined Patent Application Publication No. 2003-017121).

SUMMARY

In recent years, high performance and multi-functions of the electronicapparatuses and the like to which the secondary battery is applied areincreasingly developed. Therefore, further improvement of the batterycharacteristics has been desired.

It is desirable to provide a secondary battery capable of providingsuperior battery characteristics, a battery pack, an electric vehicle,an electric power storage system, an electric power tool, and anelectronic apparatus.

According to an embodiment of the present application, there is provideda secondary battery including: a cathode; an anode; and a gelelectrolyte. The gel electrolyte includes an electrolytic solution and apolymer compound. The electrolytic solution includes an unsaturatedcyclic ester carbonate represented by the following Formula (1),

where X is a divalent group in which m number of >C═CR1-R2 and n numberof >CR3R4 are bonded in any order; each of R1 to R4 is one of a hydrogengroup, a halogen group, a monovalent hydrocarbon group, a monovalenthalogenated hydrocarbon group, a monovalent oxygen-containinghydrocarbon group, and a monovalent halogenated oxygen-containinghydrocarbon group; any two or more of the R1 to the R4 are allowed to bebonded to one another; and m and n satisfy m≥1 and n≥0.

According to an embodiment of the present application, there is provideda battery pack including: a secondary battery; a control sectioncontrolling a used state of the secondary battery; and a switch sectionswitching the used state of the secondary battery according to aninstruction of the control section. The secondary battery includes acathode, an anode, and a gel electrolyte. The gel electrolyte includesan electrolytic solution and a polymer compound. The electrolyticsolution includes an unsaturated cyclic ester carbonate represented bythe following Formula (1),

where X is a divalent group in which m number of >C═CR1-R2 and n numberof >CR3R4 are bonded in any order; each of R1 to R4 is one of a hydrogengroup, a halogen group, a monovalent hydrocarbon group, a monovalenthalogenated hydrocarbon group, a monovalent oxygen-containinghydrocarbon group, and a monovalent halogenated oxygen-containinghydrocarbon group; any two or more of the R1 to the R4 are allowed to bebonded to one another; and m and n satisfy m≥1 and n≥0.

According to an embodiment of the present application, there is providedan electric vehicle including: a secondary battery; a conversion sectionconverting electric power supplied from the secondary battery into drivepower; a drive section operating according to the drive power; and acontrol section controlling a used state of the secondary battery. Thesecondary battery includes a cathode, an anode, and a gel electrolyte.The gel electrolyte includes an electrolytic solution and a polymercompound. The electrolytic solution includes an unsaturated cyclic estercarbonate represented by the following Formula (1),

where X is a divalent group in which m number of >C═CR1-R2 and n numberof >CR3R4 are bonded in any order; each of R1 to R4 is one of a hydrogengroup, a halogen group, a monovalent hydrocarbon group, a monovalenthalogenated hydrocarbon group, a monovalent oxygen-containinghydrocarbon group, and a monovalent halogenated oxygen-containinghydrocarbon group; any two or more of the R1 to the R4 are allowed to bebonded to one another; and m and n satisfy m≥1 and n≥0.

According to an embodiment of the present application, there is providedan electric power storage system including: a secondary battery; one ormore electric devices supplied with electric power from the secondarybattery; and a control section controlling the supplying of the electricpower from the secondary battery to the one or more electric devices.The secondary battery includes a cathode, an anode, and a gelelectrolyte. The gel electrolyte includes an electrolytic solution and apolymer compound. The electrolytic solution includes an unsaturatedcyclic ester carbonate represented by the following Formula (1),

where X is a divalent group in which m number of >C═CR1-R2 and n numberof >CR3R4 are bonded in any order; each of R1 to R4 is one of a hydrogengroup, a halogen group, a monovalent hydrocarbon group, a monovalenthalogenated hydrocarbon group, a monovalent oxygen-containinghydrocarbon group, and a monovalent halogenated oxygen-containinghydrocarbon group; any two or more of the R1 to the R4 are allowed to bebonded to one another; and m and n satisfy m≥1 and n≥0.

According to an embodiment of the present application, there is providedan electric power tool including: a secondary battery; and a movablesection being supplied with electric power from the secondary battery.The secondary battery includes a cathode, an anode, and a gelelectrolyte. The gel electrolyte includes an electrolytic solution and apolymer compound. The electrolytic solution includes an unsaturatedcyclic ester carbonate represented by the following Formula (1),

where X is a divalent group in which m number of >C═CR1-R2 and n numberof >CR3R4 are bonded in any order; each of R1 to R4 is one of a hydrogengroup, a halogen group, a monovalent hydrocarbon group, a monovalenthalogenated hydrocarbon group, a monovalent oxygen-containinghydrocarbon group, and a monovalent halogenated oxygen-containinghydrocarbon group; any two or more of the R1 to the R4 are allowed to bebonded to one another; and m and n satisfy m≥1 and n≥0.

According to an embodiment of the present application, there is providedan electronic apparatus including a secondary battery as an electricpower supply source. The secondary battery includes a cathode, an anode,and a gel electrolyte, the gel electrolyte includes an electrolyticsolution and a polymer compound. The electrolytic solution includes anunsaturated cyclic ester carbonate represented by the following Formula(1),

where X is a divalent group in which m number of >C═CR1-R2 and n numberof >CR3R4 are bonded in any order; each of R1 to R4 is one of a hydrogengroup, a halogen group, a monovalent hydrocarbon group, a monovalenthalogenated hydrocarbon group, a monovalent oxygen-containinghydrocarbon group, and a monovalent halogenated oxygen-containinghydrocarbon group; any two or more of the R1 to the R4 are allowed to bebonded to one another; and m and n satisfy m≥1 and n≥0.

According to the secondary battery according to the embodiment of thepresent application, since the secondary battery includes the gelelectrolyte containing the electrolytic solution and the polymercompound, and the electrolytic solution contains the unsaturated cyclicester carbonate, superior battery characteristics are obtainable.Further, according to the battery pack, the electric vehicle, theelectric power storage system, the electric power tool, and theelectronic apparatus according to the embodiments of the presentapplication, similar effects are obtainable.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary, and are intended toprovide further explanation of the technology as claimed.

Additional features and advantages are described herein, and will beapparent from the following Detailed Description and the figures.

BRIEF DESCRIPTION OF THE FIGURES

The accompanying drawings are included to provide a furtherunderstanding of the disclosure, and are incorporated in and constitutea part of this specification. The drawings illustrate embodiments and,together with the specification, serve to explain the principles of thetechnology.

FIG. 1 is a perspective view illustrating a configuration of a secondarybattery according to an embodiment of the present application.

FIG. 2 is a cross-sectional view taken along a line II-II of a spirallywound electrode body illustrated in FIG. 1.

FIG. 3 is a block diagram illustrating a configuration of an applicationexample (battery pack) of the secondary battery.

FIG. 4 is a block diagram illustrating a configuration of an applicationexample (electric vehicle) of the secondary battery.

FIG. 5 is a block diagram illustrating a configuration of an applicationexample (electric power storage system) of the secondary battery.

FIG. 6 is a block diagram illustrating a configuration of an applicationexample (electric power tool) of the secondary battery.

DETAILED DESCRIPTION

An embodiment of the present application will be hereinafter describedin detail with reference to the drawings. The description will be givenin the following order.

1. Secondary Battery

2. Applications of Secondary Battery

2-1. Battery Pack

2-2. Electric Vehicle

2-3. Electric Power Storage System

2-4. Electric Power Tool

[1. Secondary Battery]

First, a description will be given of a secondary battery according toan embodiment of the present application.

FIG. 1 illustrates an exploded perspective configuration of a secondarybattery. FIG. 2 illustrates an enlarged cross-section taken along a lineII-II of a spirally wound electrode body 30 illustrated in FIG. 1.

[Whole Configuration of Secondary Battery]

The secondary battery herein described is a lithium ion secondarybattery in which the capacity of an anode 34 is obtained by insertionand extraction of Li (lithium ions) as an electrode reactant.

The secondary battery is what we call a laminated film type lithium ionsecondary battery. In the secondary battery, the spirally woundelectrode body 30 is contained in a film-like outer package member 40.In the spirally wound electrode body 30, a cathode 33 and the anode 34are layered with a separator 35 and an electrolyte layer 36 in betweenand are spirally wound. A cathode lead 31 is attached to the cathode 33,and an anode lead 32 is attached to the anode 34. The outermostperiphery of the spirally wound electrode body 30 is protected by aprotective tape 37.

The cathode lead 31 and the anode lead 32 are, for example, led out frominside to outside of the outer package member 40 in the same direction.The cathode lead 31 is made of, for example, a conductive material suchas Al, and the anode lead 32 is made of, for example, a conducivematerial such as Cu, Ni, and stainless steel. These conductive materialsare in the shape of, for example, a thin plate or mesh.

The outer package member 40 is a laminated film in which, for example, afusion bonding layer, a metal layer, and a surface protective layer arelaminated in this order. In the laminated film, for example, therespective outer edges of the fusion bonding layers of two films arebonded to each other by fusion bonding, an adhesive, or the like so thatthe fusion bonding layers and the spirally wound electrode body 30 areopposed to each other. Examples of the fusion bonding layer include afilm made of polyethylene, polypropylene, or the like. Examples of themetal layer include an Al foil. Examples of the surface protective layerinclude a film made of nylon, polyethylene terephthalate, or the like.

Specially, as the outer package member 40, an aluminum laminated film inwhich a polyethylene film, an Al foil, and a nylon film are laminated inthis order is preferable. However, the outer package member 40 may bemade of a laminated film having other laminated structure, a polymerfilm such as polypropylene, or a metal film.

An adhesive film 41 to protect from outside air intrusion is insertedbetween the outer package member 40, and the cathode lead 31 and theanode lead 32. The adhesive film 41 is made of a material havingadhesion characteristics with respect to the cathode lead 31 and theanode lead 32. Examples of such an adhesive material include apolyolefin resin such as polyethylene, polypropylene, modifiedpolyethylene, and modified polypropylene.

[Cathode]

The cathode 33 has, for example, a cathode active material layer 33B ona single surface or both surfaces of a cathode current collector 33A.The cathode current collector 33A may be made of, for example, aconductive material such as Al, Ni, and stainless steel.

The cathode active material layer 33B contains, as cathode activematerials, one or more of cathode materials capable of inserting andextracting lithium ions. As necessary, the cathode active material layer33B may contain other materials such as a cathode binder and a cathodeelectric conductor.

The cathode material is preferably a lithium-containing compound, sincethereby high energy density is obtained. Examples of thelithium-containing compound include a lithium transition metal compositeoxide and a lithium transition metal phosphate compound. The lithiumtransition metal composite oxide is an oxide containing Li and one ormore transition metal elements as constituent elements. The lithiumtransition metal phosphate compound is a compound containing Li and oneor more transition metal elements as constituent elements. Specially, itis preferable that the transition metal element be one or more of Co,Ni, Mn, Fe, and the like, since thereby a higher voltage is obtained.The chemical formula thereof is expressed by, for example, Li_(x)M1O₂ orLi_(y)M2PO₄. In the formula, M1 and M2 represent one or more transitionmetal elements. Values of x and y vary according to the charge anddischarge state, and are generally in the range of 0.05≤x≤1.10 and0.05≤y≤1.10.

Examples of the lithium transition metal composite oxide include LiCoO₂,LiNiO₂, and a lithium-nickel-based composite oxide represented by thefollowing Formula (20). Examples of the lithium transition metalphosphate compound include LiFePO₄ and LiFe_(1-u)Mn_(u)PO₄ (u<1), sincethereby a high battery capacity is obtained and superior cyclecharacteristics are obtained. However, a lithium transition metalcomposite oxide and a lithium transition metal phosphate compound otherthan the foregoing compounds may be used.LiNi_(1−z)M_(z)O₂  (20)

In Formula (20), M is one or more of Co, Mn, Fe, Al, V, Sn, Mg, Ti, Sr,Ca, Zr, Mo, Tc, Ru, Ta, W, Re, Yb, Cu, Zn, Ba, B, Cr, Si, Ga, P, Sb, andNb. z is in the range of 0.005<z<0.5.

In addition thereto, the cathode material may be, for example, an oxide,a disulfide, a chalcogenide, a conductive polymer, or the like. Examplesof the oxide include titanium oxide, vanadium oxide, and manganesedioxide. Examples of the disulfide include titanium disulfide andmolybdenum sulfide. Examples of the chalcogenide include niobiumselenide. Examples of the conductive polymer include sulfur,polyaniline, and polythiophene. However, the cathode material may be amaterial other than the foregoing materials as long as the material isallowed to insert and extract lithium ions.

Examples of the cathode binder include one or more of synthetic rubbers,polymer materials, and the like. Examples of the synthetic rubberinclude a styrene-butadiene-based rubber, a fluorine-based rubber, andethylene propylene diene. Examples of the polymer material includepolyvinylidene fluoride and polyimide.

Examples of the cathode electric conductor include one or more of carbonmaterials and the like. Examples of the carbon materials includegraphite, carbon black, acetylene black, and Ketjen black. The cathodeelectric conductor may be a metal material, a conductive polymer, or thelike as long as the material has electric conductivity.

[Anode]

The anode 34 has, for example, an anode active material layer 34B on asingle surface or both surfaces of an anode current collector 34A.

The anode current collector 34A may be made of, for example, aconductive material such as Cu, Ni, and stainless steel. The surface ofthe anode current collector 34A is preferably roughened. Thereby, due towhat we call an anchor effect, adhesion characteristics of the anodeactive material layer 34B with respect to the anode current collector34A are improved. In this case, it is enough that the surface of theanode current collector 34A in the region opposed to the anode activematerial layer 34B is roughened at minimum. Examples of rougheningmethods include a method of forming fine particles by electrolytictreatment. The electrolytic treatment is a method of providing concavityand convexity by forming fine particles on the surface of the anodecurrent collector 34A by an electrolytic method in an electrolytic bath.A copper foil formed by an electrolytic method is generally called“electrolytic copper foil.”

The anode active material layer 34B contains one or more of anodematerials capable of inserting and extracting lithium ions as anodeactive materials, and may also contain other materials such as an anodebinder and an anode electric conductor as necessary. Details of theanode binder and the anode electric conductor are, for example, similarto those of the cathode binder and the cathode electric conductor,respectively. The chargeable capacity of the anode material ispreferably larger than the discharge capacity of the cathode 33 in orderto prevent unintentional precipitation of lithium metal at the time ofcharge and discharge.

Examples of the anode material include a carbon material. In the carbonmaterial, its crystal structure change at the time of insertion andextraction of lithium ions is extremely small. Therefore, the carbonmaterial provides high energy density and superior cyclecharacteristics. Further, the carbon material functions as an anodeelectric conductor as well. Examples of the carbon material includegraphitizable carbon, non-graphitizable carbon in which the spacing of(002) plane is equal to or greater than 0.37 nm, and graphite in whichthe spacing of (002) plane is equal to or smaller than 0.34 nm. Morespecifically, examples of the carbon material include pyrolytic carbons,cokes, glassy carbon fiber, an organic polymer compound fired body,activated carbon, and carbon blacks. Of the foregoing, examples of thecokes include pitch coke, needle coke, and petroleum coke. The organicpolymer compound fired body is obtained by firing (carbonizing) apolymer compound such as a phenol resin and a furan resin at appropriatetemperature. In addition thereto, the carbon material may be lowcrystalline carbon or amorphous carbon heat-treated at temperature ofabout 1000° C. or less. It is to be noted that the shape of the carbonmaterial may be any of a fibrous shape, a spherical shape, a granularshape, and a scale-like shape.

Further, the anode material may be, for example, a material (metal-basedmaterial) containing one or more of metal elements and metalloidelements as constituent elements, since high energy density is therebyobtained. Such a metal-based material may be a simple substance, analloy, or a compound, may be two or more thereof, or may have one ormore phases thereof in part or all thereof. “Alloy” includes a materialcontaining one or more metal elements and one or more metalloidelements, in addition to a material configured of two or more metalelements. Further, the “alloy” may contain a nonmetallic element.Examples of the structure thereof include a solid solution, a eutecticcrystal (eutectic mixture), an intermetallic compound, and a structurein which two or more thereof coexist.

The foregoing metal element and the foregoing metalloid element may be,for example, one or more of metal elements and metalloid elementscapable of forming an alloy with Li. Specific examples thereof includeMg, B, Al, Ga, In, Si, Ge, Sn, Pb, Bi, Cd, Ag, Zn, Hf, Zr, Y, Pd, andPt. Specially, Si or Sn or both are preferably used. Si and Sn have ahigh ability of inserting and extracting lithium ions, and thereforeprovide high energy density.

A material containing Si, Sn, or both may be a simple substance, analloy, or a compound of Si or Sn; two or more thereof; or a materialhaving one or more phases thereof in part or all thereof. The simplesubstance merely refers to a general simple substance (a small amount ofimpurity may be therein contained), and does not necessarily refer to apurity 100% simple substance.

Examples of the alloys of Si include a material containing one or moreof elements such as Sn, Ni, Cu, Fe, Co, Mn, Zn, In, Ag, Ti, Ge, Bi, Sb,and Cr as constituent elements other than Si. Examples of the compoundsof Si include a material containing one or more of C, O, and the like asconstituent elements other than Si. For example, the compounds of Si maycontain one or more of the elements described for the alloys of Si asconstituent elements other than Si.

Examples of the alloys and the compounds of Si include SiB₄, SiB₆,Mg₂Si, Ni₂Si, TiSi₂, MoSi₂, CoSi₂, NiSi₂, CaSi₂, CrSi₂, Cu₅Si, FeSi₂,MnSi₂, NbSi₂, TaSi₂, VSi₂, WSi₂, ZnSi₂, SiC, Si₃N₄, Si₂N₂O, SiO_(v)(0<v≤2), and LiSiO. v in SiO_(v) may be in the range of 0.2<v<1.4.

Examples of the alloys of Sn include a material containing one or moreof elements such as Si, Ni, Cu, Fe, Co, Mn, Zn, In, Ag, Ti, Ge, Bi, Sb,and Cr as constituent elements other than Sn. Examples of the compoundsof Sn include a material containing one or more of C, O, and the like asconstituent elements. The compounds of Sn may contain, for example, oneor more of the elements described for the alloys of Sn as constituentelements other than Sn. Examples of the alloys and the compounds of Sninclude SnO_(w) (0<w≤2), SnSiO₃, LiSnO, and Mg₂Sn.

Further, as a material containing Sn, for example, a material containinga second constituent element and a third constituent element in additionto Sn as a first constituent element is preferable. Examples of thesecond constituent element include one or more of elements such as Co,Fe, Mg, Ti, V, Cr, Mn, Ni, Cu, Zn, Ga, Zr, Nb, Mo, Ag, In, Ce, Hf, Ta,W, Bi, and Si. Examples of the third constituent element include one ormore of B, C, Al, P, and the like. In the case where the secondconstituent element and the third constituent element are contained, ahigh battery capacity, superior cycle characteristics, and the like areobtained.

Specially, a material containing Sn, Co, and C as constituent elements(SnCoC-containing material) is preferable. The composition of theSnCoC-containing material is, for example, as follows. That is, the Ccontent is from 9.9 mass % to 29.7 mass % both inclusive, and the ratioof Sn and Co contents (Co/(Sn+Co)) is from 20 mass % to 70 mass % bothinclusive, since high energy density is obtained in such a compositionrange.

It is preferable that the SnCoC-containing material have a phasecontaining Sn, Co, and C. Such a phase is preferably low-crystalline oramorphous. The phase is a reaction phase capable of reacting with Li.Due to existence of the reaction phase, superior characteristics areobtained. The half bandwidth of the diffraction peak obtained by X-raydiffraction of the phase is preferably equal to or greater than 1° basedon diffraction angle of 2θ in the case where CuKα ray is used as aspecific X ray, and the insertion rate is 1°/min. Thereby, lithium ionsare more smoothly inserted and extracted, and reactivity with theelectrolytic solution is decreased. It is to be noted that, in somecases, the SnCoC-containing material includes a phase containing asimple substance or part of the respective constituent elements inaddition to the low-crystalline phase or the amorphous phase.

Whether or not the diffraction peak obtained by the X-ray diffractioncorresponds to the reaction phase capable of reacting with Li is allowedto be easily determined by comparison between X-ray diffraction chartsbefore and after electrochemical reaction with Li. For example, if theposition of the diffraction peak after electrochemical reaction with Liis changed from the position of the diffraction peak before theelectrochemical reaction with Li, the obtained diffraction peakcorresponds to the reaction phase capable of reacting with Li. In thiscase, for example, the diffraction peak of the low crystalline reactionphase or the amorphous reaction phase is seen in the range of 2θ=from20° to 50° both inclusive. Such a reaction phase has, for example, theforegoing respective constituent elements, and the low crystalline oramorphous structure thereof possibly results from existence of C mainly.

In the SnCoC-containing material, part or all of carbon as a constituentelement are preferably bonded to a metal element or a metalloid elementas other constituent element, since thereby cohesion or crystallizationof Sn and/or the like is suppressed. The bonding state of elements isallowed to be checked by, for example, X-ray photoelectron spectroscopy(XPS). In a commercially-available device, for example, as a soft X ray,Al-Kα ray, Mg-Kα ray, or the like is used. In the case where part or allof C are bonded to a metal element, a metalloid element, or the like,the peak of a synthetic wave of 1 s orbit of carbon (Cis) is shown in aregion lower than 284.5 eV. In the device, energy calibration is made sothat the peak of 4f orbit of Au atom (Au4f) is obtained in 84.0 eV. Atthis time, in general, since surface contamination carbon exists on thematerial surface, the peak of C1s of the surface contamination carbon isregarded as 284.8 eV, which is used as the energy standard. In XPSmeasurement, the waveform of the peak of C1s is obtained as a formincluding the peak of the surface contamination carbon and the peak ofcarbon in the SnCoC-containing material. Therefore, for example,analysis is made by using commercially-available software to isolateboth peaks from each other. In the waveform analysis, the position ofthe main peak existing on the lowest bound energy side is the energystandard (284.8 eV).

It is to be noted that the SnCoC-containing material is not limited tothe material configured of only Sn, Co, and C (SnCoC). That is, theSnCoC-containing material may further contain, for example, one or moreof Si, Fe, Ni, Cr, In, Nb, Ge, Ti, Mo, Al, P, Ga, Bi, and the like asconstituent elements as necessary.

In addition to the SnCoC-containing material, a material containing Sn,Co, Fe, and C as constituent elements (SnCoFeC-containing material) isalso preferable. The composition of the SnCoFeC-containing material maybe set as any composition. For example, the composition in which the Fecontent is set small is as follows. That is, the C content is from 9.9mass % to 29.7 mass % both inclusive, the Fe content is from 0.3 mass %to 5.9 mass % both inclusive, and the ratio of contents of Sn and Co(Co/(Sn+Co)) is from 30 mass % to 70 mass % both inclusive. Further, forexample, the composition in which the Fe content is set large is asfollows. That is, the C content is from 11.9 mass % to 29.7 mass % bothinclusive, the ratio of contents of Sn, Co, and Fe ((Co+Fe)/(Sn+Co+Fe))is from 26.4 mass % to 48.5 mass % both inclusive, and the ratio ofcontents of Co and Fe (Co/(Co+Fe)) is from 9.9 mass % to 79.5 mass %both inclusive. In such a composition range, high energy density isobtained. The physical properties (such as half bandwidth) of theSnCoFeC-containing material are similar to those of the foregoingSnCoC-containing material.

In addition thereto, the anode material may be, for example, a metaloxide, a polymer compound, or the like. Examples of the metal oxideinclude iron oxide, ruthenium oxide, and molybdenum oxide. Examples ofthe polymer compound include polyacetylene, polyaniline, andpolypyrrole.

The anode active material layer 34B is formed by, for example, a coatingmethod, a vapor-phase deposition method, a liquid-phase depositionmethod, a spraying method, a firing method (sintering method), or acombination of two or more of these methods. The coating method is amethod in which, for example, after a particulate (powder) anode activematerial is mixed with an anode binder and/or the like, the mixture isdispersed in a solvent such as an organic solvent, and the anode currentcollector is coated with the resultant. Examples of the vapor-phasedeposition method include a physical deposition method and a chemicaldeposition method. Specifically, examples thereof include a vacuumevaporation method, a sputtering method, an ion plating method, a laserablation method, a thermal chemical vapor deposition method, a chemicalvapor deposition (CVD) method, and a plasma chemical vapor depositionmethod. Examples of the liquid-phase deposition method include anelectrolytic plating method and an electroless plating method. Thespraying method is a method in which an anode active material in a fusedstate or a semi-fused state is sprayed. The firing method is, forexample, a method in which after the anode current collector is coatedby a coating method, heat treatment is performed at temperature higherthan the melting point of the anode binder and/or the like. Examples ofthe firing method include a publicly-known technique such as anatmosphere firing method, a reactive firing method, and a hot pressfiring method.

In the secondary battery, as described above, in order to preventlithium metal from being unintentionally precipitated on the anode 34 inthe middle of charge, the electrochemical equivalent of the anodematerial capable of inserting and extracting lithium ions is larger thanthe electrochemical equivalent of the cathode. Further, in the casewhere the open circuit voltage (that is, a battery voltage) at the timeof completely-charged state is equal to or greater than 4.25 V, theextraction amount of lithium ions per unit mass is larger than that inthe case where the open circuit voltage is 4.20 V even if the samecathode active material is used. Therefore, amounts of the cathodeactive material and the anode active material are adjusted accordingly.Thereby, high energy density is obtainable.

[Separator]

The separator 35 separates the cathode 33 from the anode 34, and passeslithium ions while preventing current short circuit resulting fromcontact of both electrodes. The separator 35 is, for example, a porousfilm made of a synthetic resin, ceramics, or the like. The separator 35may be a laminated film in which two or more types of porous films arelaminated. Examples of the synthetic resin includepolytetrafluoroethylene, polypropylene, and polyethylene.

In particular, the separator 35 may include, for example, the foregoingporous film (base material layer) and a polymer compound layer providedon one surface or both surfaces of the base material layer. Thereby,adhesion characteristics of the separator 35 with respect to the cathode33 and the anode 34 are improved, and therefore skewness of the spirallywound electrode body 30 as a spirally wound body is suppressed. Thereby,a decomposition reaction of the electrolytic solution is suppressed, andliquid leakage of the electrolytic solution with which the base materiallayer is impregnated is suppressed. Accordingly, even if charge anddischarge are repeated, the resistance of the secondary battery is lesslikely to be increased, and battery swollenness is suppressed.

The polymer compound layer contains, for example, a polymer materialsuch as polyvinylidene fluoride, since such a polymer material has asuperior physical strength and is electrochemically stable. However, thepolymer material may be a material other than polyvinylidene fluoride.The polymer compound layer is formed as follows, for example. That is,after a solution in which the polymer material is dissolved is prepared,the surface of the base material layer is coated with the solution, andthe resultant is subsequently dried. Alternatively, the base materiallayer may be soaked in the solution and may be subsequently dried.

[Electrolyte Layer]

The electrolyte layer 36 contains an electrolytic solution and a polymercompound. That is, in the electrolyte layer 36, the electrolyticsolution is held by the polymer compound. The electrolyte layer 36 iswhat we call a gel electrolyte, since thereby high ion conductivity (forexample, 1 mS/cm or more at room temperature) is obtained and liquidleakage of the electrolytic solution is prevented. The electrolyte layer36 may contain other materials such as an additive as necessary.

Examples of the polymer compound include one or more ofpolyacrylonitrile, polyvinylidene fluoride, polytetrafluoroethylene,polyhexafluoropropylene, polyethylene oxide, polypropylene oxide,polyphosphazene, polysiloxane, polyvinyl fluoride, polyvinyl acetate,polyvinyl alcohol, polymethacrylic acid methyl, polyacrylic acid,polymethacrylic acid, styrene-butadiene rubber, nitrile-butadienerubber, polystyrene, polycarbonate, and a copolymer of vinylidenefluoride and hexafluoro propylene. Specially, polyvinylidene fluoride orthe copolymer of vinylidene fluoride and hexafluoro propylene ispreferable, and polyvinylidene fluoride is more preferable, since such apolymer compound is electrochemically stable.

[Electrolytic Solution]

The electrolytic solution contains one or more of unsaturated cyclicester carbonates represented by the following Formula (1). However, theelectrolytic solution may contain other materials such as a solvent andan electrolyte salt.

In Formula (1), X is a divalent group in which m number of >C═CR1-R2 andn number of >CR3R4 are bonded in any order. Each of R1 to R4 is one of ahydrogen group, a halogen group, a monovalent hydrocarbon group, amonovalent halogenated hydrocarbon group, a monovalent oxygen-containinghydrocarbon group, and a monovalent halogenated oxygen-containinghydrocarbon group. Any two or more of R1 to R4 may be bonded to oneanother. m and n satisfy m≥1 and n≥0.

The unsaturated cyclic ester carbonate refers to a cyclic estercarbonate having one or more carbon-carbon double bonds (>C═C<). Theelectrolytic solution contains the unsaturated cyclic ester carbonate.One reason for this is that, in this case, even if the electrolyte as amedium for a charge and discharge reaction is gelatinous, the chemicalstability of the electrolytic solution is spectacularly improved.Thereby, a decomposition reaction of the electrolytic solution issignificantly suppressed, and therefore battery characteristics such ascycle characteristics and conservation characteristics are improved.

More specifically, in the case where a liquid electrolyte (electrolyticsolution) is used, a decomposition reaction of the electrolytic solutionrarely matters at the time of charge and discharge. Therefore, batterycharacteristics are rarely affected by presence of the unsaturatedcyclic ester carbonate in the electrolytic solution.

Meanwhile, in the case where the gel electrolyte (electrolyte layer 36)is used, at the time of charge and discharge, a decomposition reactionof the electrolytic solution is significant. Therefore, batterycharacteristics largely vary according to presence of the unsaturatedcyclic ester carbonate in the electrolytic solution. In this case, ifthe electrolytic solution does not contain the unsaturated cyclic estercarbonate, a decomposition reaction of the electrolytic solution easilyproceeds, and accordingly battery characteristics are lowered. Such atendency is significant particularly under strict conditions such as ahigh-temperature environment. However, if the electrolytic solutioncontains the unsaturated cyclic ester carbonate, a rigid film resultingfrom the unsaturated cyclic ester carbonate is formed on the surface ofthe anode 34 at the time of charge and discharge, and therefore theanode 34 is protected from the electrolytic solution. Thereby, adecomposition reaction of the electrolytic solution is less likely to bepromoted, and battery characteristics are easily retained.

X in Formula (1) is a group obtained by bonding m number of >C═CR1-R2 ton number of >CR3R4 so that the valency becomes divalent as a whole (onebonding hand exists on each of both ends). Adjacent groups (groupsbonded to each other) may be the same type of group such as >C═CR1-R2and >C═CR1-R2, or may be different from each other such as >C═CR1-R2and >CR3R4. That is, the number (m) of >C═CR1-R2 used for forming thedivalent group and the number (n) of >CR3R4 used for forming thedivalent group may be any number, and the bonding order thereof may alsobe any order.

While >C═CR1-R2 is a divalent unsaturated group having the foregoingcarbon-carbon double bond, >CR3R4 is a divalent saturated group nothaving a carbon-carbon double bond. Since n satisfies n≥0, >CR3R4 as asaturated group is not necessarily included in X. Meanwhile, since msatisfies m≥1, one or more >C=CR1-R2 as a saturated group are includedin X typically. Therefore, X may be configured of only >C═CR1-R2, or maybe configured of both >C═CR1-R2 and >CR3R4. One reason for this is thatthe unsaturated cyclic ester carbonate should have one or moreunsaturated groups in the chemical structure thereof.

Values of m and n are not particularly limited as long as the conditionsof m≥1 and n≥0 are satisfied. Specially, in the case where >C═CR1-R2 is>C═CH₂ and >CR3R4 is >CH₂, (m+n)≤5 is preferably satisfied. One reasonfor this is that, in this case, the carbon number of X is notexcessively large, and therefore the solubility and the compatibility ofthe unsaturated cyclic ester carbonate are secured.

It is to be noted that any two or more of R1 to R4 in >C═CR1-R2and >CR3R4 may be bonded to one another, and the bonded groups may forma ring. As an example, R1 may be bonded to R2, R3 may be bonded to R4,and R2 may be bonded to R3 or R4.

Details of R1 to R4 are described below. R1 to R4 may be the same typeof group, or may be groups of types different from each other. Any twoor three of R1 to R4 may be the same type of group.

Each type of R1 to R4 is not particularly limited as long as each of R1to R4 is one of a hydrogen group, a halogen group, a monovalenthydrocarbon group, a monovalent halogenated hydrocarbon group, amonovalent oxygen-containing hydrocarbon group, and a monovalenthalogenated oxygen-containing hydrocarbon group. One reason for this isthat, since in this case, X has one or more carbon-carbon double bonds(>C═CR1-R2), the foregoing advantage is obtainable without depending onthe types of R1 to R4.

The halogen group is, for example, one or more of a fluorine group (—F),a chlorine group (—Cl), a bromine group (—Br), an iodine group (—I), andthe like. Specially, the fluorine group is preferable, since a filmresulting from the unsaturated cyclic ester carbonate is thereby easilyformed.

“Hydrocarbon group” is a generic term used to refer to groups configuredof C and H, and may have a straight-chain structure or a branchedstructure having one or more side chains. Examples of the monovalenthydrocarbon group include an alkyl group with carbon number from 1 to 12both inclusive, an alkenyl group with carbon number from 2 to 12 bothinclusive, an alkynyl group with carbon number from 2 to 12 bothinclusive, an aryl group with carbon number from 6 to 18 both inclusive,and a cycloalkyl group with carbon number from 3 to 18 both inclusive.One reason for this is that the foregoing advantage is thereby obtainedwhile the solubility, the compatibility, and the like of the unsaturatedcyclic ester carbonate are secured.

More specific examples of the alkyl group include a methyl group (—CH₃),an ethyl group (—C₂H₅), and a propyl group (—C₃H₇). Examples of thealkenyl group include a vinyl group (—CH═CH₂) and an allyl group(—CH₂—CH═CH₂). Examples of the alkynyl group include an ethynyl group(—C≡CH). Examples of the aryl group include a phenyl group and a naphtylgroup. Examples of the cycloalkyl group include a cyclopropyl group, acyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptylgroup, and a cyclooctyl group.

“Oxygen-containing hydrocarbon group” is a group configured of Otogether with C and H. Examples of the monovalent oxygen-containinghydrocarbon group include an alkoxy group with carbon number from 1 to12 both inclusive. One reason for this is that the foregoing advantageis thereby obtained while the solubility, the compatibility, and thelike of the unsaturated cyclic ester carbonate are secured. Morespecific examples of the alkoxy group include a methoxy group (—OCH₃)and an ethoxy group (—OC₂H₅).

It is to be noted that a group obtained by bonding two or more of theforegoing alkyl group and the like so that the whole valency becomesmonovalent may be used. Examples thereof include a group obtained bybonding an alkyl group to an aryl group and a group obtained by bondingan alkyl group to a cycloalkyl group. More specific examples of thegroup obtained by bonding an alkyl group to an aryl group include abenzil group.

“Halogenated hydrocarbon group” is obtained by substituting(halogenating) each of part or all of hydrogen groups (—H) out of theforegoing hydrocarbon group by a halogen group. Types of the halogengroup thereof are as described above. Similarly, “halogenatedoxygen-containing hydrocarbon group” is obtained by substituting each ofpart or all of hydrogen groups out of the foregoing oxygen-containinghydrocarbon group by a halogen group. Types of the halogen group thereofare as described above.

Examples of the monovalent halogenated hydrocarbon group include a groupobtained by halogenating the foregoing alkyl group or the like, forexample. That is, the monovalent halogenated hydrocarbon group is agroup obtained by substituting each of part or all of hydrogen groups ofthe foregoing alkyl group or the like by a halogen group. More specificexamples of the group obtained by halogenating an alkyl group or thelike include a trifluoromethyl group (—CF₃) and a pentafluoroethyl group(—C₂F₅). Further, examples of the monovalent halogenatedoxygen-containing hydrocarbon group include a group obtained bysubstituting each of part or all of hydrogen groups of the foregoingalkoxy group or the like by a halogen group. More specific examples ofthe group obtained by halogenating an alkoxy group or the like include atrifluoromethoxy group (—OCF₃) and a pentafluoroethoxy group (—OC₂F₅).

It is to be noted that each of R1 to R4 may be a group other than theforegoing groups. Specifically, each of R1 to R4 may be, for example, aderivative of each of the foregoing groups. The derivative is obtainedby introducing one or more substituent groups to each of the foregoinggroups. Substituent group types may be arbitrary.

Specially, the unsaturated cyclic ester carbonate is preferablyrepresented by the following Formula (2) or Formula (3). One reason forthis is that, in this case, the foregoing advantage is obtained, andsuch compounds are easily synthesized.

In Formulas (2) and (3), each of R5 to R10 is one of a hydrogen group, ahalogen group, a monovalent hydrocarbon group, a monovalent halogenatedhydrocarbon group, a monovalent oxygen-containing hydrocarbon group, anda monovalent halogenated oxygen-containing hydrocarbon group. R5 and R6may be bonded to each other; and arbitrary two or more of R7 to R10 maybe bonded to one another.

Focusing attention on a relation between Formula (1) and Formula (2),the unsaturated cyclic ester carbonate represented by Formula (2) has,as X in Formula (1), one unsaturated group (>C═CH₂) correspondingto >C═CR1-R2 and one saturated group (>CR5R6) corresponding to >CR3R4.Meanwhile, focusing attention on a relation between Formula (1) andFormula (3), the unsaturated cyclic ester carbonate represented byFormula (3) has, as X, one unsaturated group (>C═CH₂) correspondingto >C═CR1-R2 and two saturated groups (>CR7R8 and >CR9R10) correspondingto >CR3R4. However, the foregoing one unsaturated group and theforegoing two saturated groups are bonded in order of >CR7R8, >CR9R10,and >C═CH₂.

Details of R5 and R6 in Formula (2) and R7 to R10 in Formula (3) aresimilar to those of R1 to R4 in Formula (1), and therefore, descriptionsthereof will be omitted.

Specific examples of the unsaturated cyclic ester carbonate includecompounds represented by Formula (1-1) to Formula (1-56) describedbelow. Such unsaturated cyclic ester carbonates include a geometricisomer. However, specific examples of the unsaturated cyclic estercarbonate are not limited to the compounds listed in Formula (1-1) toFormula (1-56).

Specially, Formula (1-1) etc. corresponding to Formula (2) or Formula(1-3) etc. corresponding to Formula (3) are preferable, since thereby ahigher effect is obtainable.

Although the content of the unsaturated cyclic ester carbonate in theelectrolytic solution is not particularly limited, specially, thecontent thereof is preferably from 0.01 wt % to 10 wt % both inclusive,and more preferably from 0.1 wt % to 5 wt % both inclusive since therebya higher effect is obtainable.

The solvent used for the electrolytic solution contains one or more ofnonaqueous solvents such as an organic solvent (other than the foregoingunsaturated cyclic ester carbonate).

Examples of the nonaqueous solvents include a cyclic ester carbonate, achain ester carbonate, lactone, a chain carboxylic ester, and nitrile,since thereby a superior battery capacity, superior cyclecharacteristics, superior conservation characteristics, and the like areobtained. Examples of the cyclic ester carbonate include ethylenecarbonate, propylene carbonate, and butylene carbonate. Examples of thechain ester carbonate include dimethyl carbonate, diethyl carbonate,ethyl methyl carbonate, and methylpropyl carbonate. Examples of thelactone include γ-butyrolactone and γ-valerolactone. Examples of thecarboxylic ester include methyl acetate, ethyl acetate, methylpropionate, ethyl propionate, methyl butyrate, methyl isobutyrate,methyl trimethylacetate, and ethyl trimethylacetate. Examples of thenitrile include acetonitrile, glutaronitrile, adiponitrile,methoxyacetonitrile, and 3-methoxypropionitrile.

In addition thereto, the nonaqueous solvent may be 1,2-dimethoxyethane,tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran,1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,3-dioxane, 1,4-dioxane,N,N-dimethylformamide, N-methylpyrrolidinone, N-methyloxazolidinone,N,N′-dimethylimidazolidinone, nitromethane, nitroethane, sulfolane,trimethyl phosphate, and dimethyl sulfoxide. Thereby, a superior batterycapacity and the like are similarly obtained.

Specially, one or more of ethylene carbonate, propylene carbonate,dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate arepreferable, since thereby a superior battery capacity, superior cyclecharacteristics, superior conservation characteristics, and the like areobtained. In this case, a combination of a high viscosity (highdielectric constant) solvent (for example, specific dielectric constantε≥30) such as ethylene carbonate and propylene carbonate and a lowviscosity solvent (for example, viscosity≤1 mPa·s) such as dimethylcarbonate, ethylmethyl carbonate, and diethyl carbonate is morepreferable. One reason for this is that the dissociation property of theelectrolyte salt and ion mobility are improved.

In particular, the solvent preferably contains one or more of otherunsaturated cyclic ester carbonates represented by Formula (4) andFormula (5) described below. One reason for this is that a stableprotective film is formed mainly on the surface of the anode 34 at thetime of charge and discharge, and therefore a decomposition reaction ofthe electrolytic solution is suppressed. R11 and R12 may be the sametype of group, or may be groups different from each other. Further, R13to R16 may be the same type of group, or may be groups different fromeach other. Alternatively, part of R13 to R16 may be the same type ofgroup. The content of other unsaturated cyclic ester carbonate in thesolvent is not particularly limited, and is, for example, from 0.01 wt %to 10 wt % both inclusive. However, specific examples of otherunsaturated cyclic ester carbonate are not limited to theafter-mentioned compounds, and other compounds corresponding to Formula(4) and Formula (5) may be used.

In Formula (4), each of R11 and R12 is one of a hydrogen group and analkyl group.

In Formula (5), each of R13 to R16 is one of a hydrogen group, an alkylgroup, a vinyl group, and an allyl group. One or more of R13 to R16 eachare a vinyl group or an allyl group.

Other unsaturated cyclic ester carbonate represented by Formula (4) is avinylene-carbonate-based compound. Each type of R11 and R12 is notparticularly limited as long as each of R11 and R12 is one of a hydrogengroup and an alkyl group. Examples of the alkyl group include a methylgroup and an ethyl group, and the carbon number of the alkyl group ispreferably from 1 to 12 both inclusive, since superior solubility andsuperior compatibility are thereby obtained. Specific examples of thevinylene-carbonate-based compounds include vinylene carbonate(1,3-dioxole-2-one), methylvinylene carbonate(4-methyl-1,3-dioxole-2-one), ethylvinylene carbonate(4-ethyl-1,3-dioxole-2-one), 4,5-dimethyl-1,3-dioxole-2-one, and4,5-diethyl-1,3-dioxole-2-one. It is to be noted that each of R11 andR12 may be a group obtained by substituting each of part or all ofhydrogen groups of the alkyl group by a halogen group. In this case,specific examples of the vinylene-carbonate-based compounds include4-fluoro-1,3-dioxole-2-one and 4-trifluoromethyl-1,3-dioxole-2-one.Specially, vinylene carbonate is preferable, since vinylene carbonate iseasily available and provides a high effect.

Other unsaturated cyclic ester carbonate represented by Formula (5) is avinylethylene-carbonate-based compound. Each type of R13 to R16 is notparticularly limited as long as each of R13 to R16 is one of a hydrogengroup, an alkyl group, a vinyl group, and an allyl group, where one ormore of R13 to R16 are each one of a vinyl group and an allyl group. Thetype and the carbon number of the alkyl group are similar to those ofR11 and R12. Specific examples of the vinylethylene-carbonate-basedcompounds include vinylethylene carbonate (4-vinyl-1,3-dioxolane-2-one),4-methyl-4-vinyl-1,3-dioxolane-2-one,4-ethyl-4-vinyl-1,3-dioxolane-2-one,4-n-propyl-4-vinyl-1,3-dioxolane-2-one,5-methyl-4-vinyl-1,3-dioxolane-2-one, 4,4-divinyl-1,3-dioxolane-2-one,and 4,5-divinyl-1,3-dioxolane-2-one. Specially, vinylethylene carbonateis preferable, since vinylethylene carbonate is easily available, andprovides a high effect. It is needless to say that all of R13 to R16 maybe vinyl groups or allyl groups. Alternatively, some of R13 to R16 maybe vinyl groups, and the others thereof may be allyl groups.

It is to be noted that other unsaturated cyclic ester carbonate may bethe compounds represented by Formula (4) and Formula (5), or may becatechol carbonate having a benzene ring.

Further, the solvent preferably contains one or more of halogenatedester carbonates represented by the following Formula (6) and Formula(7). One reason for this is that a stable protective film is formedmainly on the surface of the anode 34 at the time of charge anddischarge, and therefore a decomposition reaction of the electrolyticsolution is suppressed. The halogenated ester carbonate represented byFormula (6) is a cyclic ester carbonate having one or more halogens asconstituent elements (halogenated cyclic ester carbonate). Thehalogenated ester carbonate represented by Formula (7) is a chain estercarbonate having one or more halogens as constituent elements(halogenated chain ester carbonate). R18 to R21 may be the same type ofgroup, or may be groups of types different from each other.Alternatively, part of R18 to R21 may be the same type of group. Thesame is applied to R22 to R27. Although the content of the halogenatedester carbonate in the solvent is not particularly limited, the contentthereof is, for example, from 0.01 wt % to 50 wt % both inclusive.However, specific examples of the halogenated ester carbonate are notlimited to the compounds described below, and other compoundscorresponding to Formula (6) and Formula (7) may be used.

In Formula (6), each of R17 to R20 is one of a hydrogen group, a halogengroup, an alkyl group, and a halogenated alkyl group. One or more of R17to R20 are each one of a halogen group and a halogenated alkyl group.

In Formula (7), each of R21 to R26 is one of a hydrogen group, a halogengroup, an alkyl group, and a halogenated alkyl group. One or more of R21to R26 are each a halogen group or a halogenated alkyl group.

Although halogen type is not particularly limited, specially, fluorine(—F), chlorine (—Cl), or bromine (Br) is preferable, and fluorine ismore preferable since thereby a higher effect is obtained compared toother halogens. However, the number of halogens is more preferably twothan one, and further may be three or more. One reason for this is that,since thereby an ability of forming a protective film is improved and amore rigid and stable protective film is formed, a decompositionreaction of the electrolytic solution is thereby more suppressed.

Examples of the halogenated cyclic ester carbonate include compoundsrepresented by the following Formula (6-1) to Formula (6-21). Thehalogenated cyclic ester carbonate includes a geometric isomer.Specially, 4-fluoro-1,3-dioxolane-2-one represented by Formula (6-1) or4,5-difluoro-1,3-dioxolane-2-one represented by Formula (6-3) ispreferable, and the latter is more preferable. Further, as4,5-difluoro-1,3-dioxolane-2-one, a trans isomer is more preferable thana cis isomer, since the trans isomer is easily available and provides ahigh effect. Examples of the halogenated chain ester carbonate includefluoromethyl methyl carbonate, bis (fluoromethyl) carbonate, anddifluoromethyl methyl carbonate.

Further, the solvent preferably contains sultone (cyclic sulfonicester), since thereby the chemical stability of the electrolyticsolution is more improved. Examples of sultone include propane sultoneand propene sultone. Although the sultone content in the solvent is notparticularly limited, for example, the sultone content is from 0.5 wt %to 5 wt % both inclusive. Specific examples of sultone are not limitedto the foregoing compounds, and may be other compounds.

Further, the solvent preferably contains an acid anhydride since thechemical stability of the electrolytic solution is thereby furtherimproved. Examples of the acid anhydrides include a carboxylicanhydride, a disulfonic anhydride, and a carboxylic acid sulfonic acidanhydride. Examples of the carboxylic anhydride include a succinicanhydride, a glutaric anhydride, and a maleic anhydride. Examples of thedisulfonic anhydride include an ethane disulfonic anhydride and apropane disulfonic anhydride. Examples of the carboxylic acid sulfonicacid anhydride include a sulfobenzoic anhydride, a sulfopropionicanhydride, and a sulfobutyric anhydride. Although the content of theacid anhydride in the solvent is not particularly limited, for example,the content thereof is from 0.5 wt % to 5 wt % both inclusive. However,specific examples of the acid anhydrides are not limited to theforegoing compounds, and other compound may be used.

The electrolyte salt used for the electrolytic solution may contain, forexample, one or more of salts such as a lithium salt. However, theelectrolyte salt may contain, for example, a salt other than the lithiumsalt (for example, a light metal salt other than the lithium salt).

Examples of the lithium salts include lithium hexafluorophosphate(LiPF₆), lithium tetrafluoroborate (LiBF₄), lithium perchlorate(LiClO₄), lithium hexafluoroarsenate (LiAsF₆), lithium tetraphenylborate(LiB(C₆H₅)₄), lithium methanesulfonate (LiCH₃SO₃), lithiumtrifluoromethane sulfonate (LiCF₃SO₃), lithium tetrachloroaluminate(LiAlCl₄), dilithium hexafluorosilicate (Li₂SiF₆), lithium chloride(LiCl), and lithium bromide (LiBr). Thereby, a superior batterycapacity, superior cycle characteristics, superior conservationcharacteristics, and the like are obtained. However, specific examplesof the lithium salt are not limited to the foregoing compounds, and maybe other compounds.

Specially, one or more of LiPF₆, LiBF₄, LiClO₄, and LiAsF₆ arepreferable, and LiPF₆ is more preferable, since the internal resistanceis thereby lowered, and therefore, a higher effect is obtained.

In particular, the electrolyte salt preferably contains one or more ofcompounds represented by the following Formula (8) to Formula (10),since thereby, a higher effect is obtained. It is to be noted that R31and R33 may be the same type of group, or may be groups of typesdifferent from each other. The same is applied to R41 to R43 and to R51and R52. However, specific examples of the compounds represented byFormula (8) to Formula (10) are not limited to the after-mentionedcompounds, and other compounds corresponding to Formula (8) to Formula(10) may be used.

In Formula (8), X31 is one of Group 1 elements, Group 2 elements in thelong-period periodic table, and A1. M31 is one of transition metals,Group 13 elements, Group 14 elements, and Group 15 elements in thelong-period periodic table. R31 is a halogen group. Y31 is one of—C(═O)—R32-C(═O)—, —C(═O)—CR33₂-, and —C(═O)—C(═O)—. R32 is one of analkylene group, a halogenated alkylene group, an arylene group, and ahalogenated arylene group. R33 is one of an alkyl group, a halogenatedalkyl group, an aryl group, and a halogenated aryl group. a3 is one ofinteger numbers 1 to 4 both inclusive. b3 is one of integer numbers 0,2, and 4. Each of c3, d3, m3, and n3 is one of integer numbers 1 to 3both inclusive.

In Formula (9), X41 is one of Group 1 elements and Group 2 elements inthe long-period periodic table. M41 is one of transition metals, Group13 elements, Group 14 elements, and Group 15 elements in the long-periodperiodic table. Y41 is one of —C(═O)—(CR41₂)_(b4)-C(═O)—,—R43₂C—(CR42₂)_(c4)-C(═O)—, —R43₂C—(CR42₂)_(c4)-CR43₂-,—R43₂C—(CR42₂)_(c4)-S(═O)₂—, —S(═O)₂—(CR42₂)_(d4)-S(═O)₂—, and—C(═O)—(CR42₂)_(d4)-S(═O)₂—. Each of R41 and R43 is one of a hydrogengroup, an alkyl group, a halogen group, and a halogenated alkyl group.One or more of R41 and R43 are each the halogen group or the halogenatedalkyl group. R42 is one of a hydrogen group, an alkyl group, a halogengroup, and a halogenated alkyl group. Each of a4, e4, and n4 is one ofinteger numbers 1 and 2. Each of b4 and d4 is one of integer numbers 1to 4 both inclusive. c4 is one of integer numbers 0 to 4 both inclusive.Each of f4 and m4 is one of integer numbers 1 to 3 both inclusive.

In Formula (10), X51 is one of Group 1 elements and Group 2 elements inthe long-period periodic table. M51 is one of transition metals, Group13 elements, Group 14 elements, and Group 15 elements in the long-periodperiodic table. Rf is one of a fluorinated alkyl group with carbonnumber from 1 to 10 both inclusive and a fluorinated aryl group withcarbon number from 1 to 10 both inclusive. Y51 is one of—C(═O)—(CR51₂)_(d5)-C(═O)— —R52₂C—(CR51₂)_(d5)-C(═O)—, —R52₂C—(CR51₂)_(d5)-CR52₂-, —R52₂C—(CR51₂)_(d5)-S(═O)₂—,—S(═O)₂—(CR51₂)_(e5)-S(═O)₂—, and —C(═O)—(CR51₂)_(e5)-S(═O)₂—. R51 isone of a hydrogen group, an alkyl group, a halogen group, and ahalogenated alkyl group. R52 is one of a hydrogen group, an alkyl group,a halogen group, and a halogenated alkyl group, and one or more thereofeach are a halogen group or a halogenated alkyl group. Each of a5, f5,and n5 is one of integer numbers 1 and 2. Each of b5, c5, and e5 is oneof integer numbers 1 to 4 both inclusive. d5 is one of integer numbers 0to 4 both inclusive. Each of g5 and m5 is one of integer numbers 1 to 3both inclusive.

It is to be noted that Group 1 elements include H, Li, Na, K, Rb, Cs,and Fr. Group 2 elements include Be, Mg, Ca, Sr, Ba, and Ra. Group 13elements include B, Al, Ga, In, and Tl. Group 14 elements include C, Si,Ge, Sn, and Pb. Group 15 elements include N, P, As, Sb, and Bi.

Examples of the compound represented by Formula (8) include compoundsrepresented by Formula (8-1) to Formula (8-6). Examples of the compoundrepresented by Formula (9) include compounds represented by Formula(9-1) to Formula (9-8). Examples of the compound represented by Formula(10) include a compound represented by Formula (10-1).

Further, the electrolyte salt preferably contains one or more ofcompounds represented by the following Formula (11) to Formula (13),since thereby, a higher effect is obtained. m and n may be the samevalue or values different from each other. The same is applied to p, q,and r. However, specific examples of the compounds represented byFormula (11) to Formula (13) are not limited to compounds describedbelow and other compounds corresponding to Formula (11) to Formula (13)may be used.LiN(C_(m)F_(2m+1)SO₂)(C_(n)F_(2n+1)SO₂)  (11)

In Formula (11), each of m and n is an integer number equal to orgreater than 1.

In Formula (12), R61 is a straight-chain or branched perfluoro alkylenegroup with carbon number from 2 to 4 both inclusive.LiC(C_(p)F_(2p+1)SO₂)(C_(q)F_(2q+1)SO₂)(C_(r)F_(2r+1)SO₂)  (13)

In Formula (13), each of p, q, and r is an integer number equal to orgreater than 1.

The compound represented by Formula (11) is a chain imide compound.Examples thereof include lithium bis(trifluoromethanesulfonyl)imide

-   (LiN(CF₃SO₂)₂), lithium bis(pentafluoroethanesulfonyl)imide    (LiN(C₂F₅SO₂)₂),-   lithium (trifluoromethanesulfonyl)(pentafluoroethanesulfonyl)imide    (LiN(CF₃SO₂)(C₂F₅SO₂)),-   lithium(trifluoromethanesulfonyl)(heptafluoropropanesulfonyl)imide    (LiN(CF₃SO₂)(C₃F₇SO₂)), and-   lithium(trifluoromethanesulfonyl)(nonafluorobutanesulfonyl)imide    (LiN(CF₃SO₂)(C₄F₉SO₂)).

The compound represented by Formula (12) is a cyclic imide compound.Examples thereof include compounds represented by Formula (12-1) toFormula (12-4).

The compound represented by Formula (13) is a chain methyde compound.Examples thereof include lithium tris(trifluoromethanesulfonyl)methyde(LiC(CF₃SO₂)₃).

Although the content of the electrolyte salt is not particularlylimited, specially, the content thereof is preferably from 0.3 mol/kg to3.0 mol/kg both inclusive with respect to the nonaqueous solvent, sincethereby high ion conductivity is obtained.

[Operation of Secondary Battery]

In the secondary battery, for example, at the time of charge, lithiumions extracted from the cathode 33 are inserted in the anode 34 throughthe electrolyte layer 36. Further, at the time of discharge, lithiumions extracted from the anode 34 are inserted in the cathode 33 throughthe electrolyte layer 36.

[Method of Manufacturing Secondary Battery]

The secondary battery including the gel electrolyte layer 36 ismanufactured, for example, by the following three types of procedures.

In the first procedure, first, the cathode 33 is formed. A cathodeactive material is mixed with a cathode binder, a cathode electricconductor, and/or the like as necessary to prepare a cathode mixture.Subsequently, the cathode mixture is dispersed in an organic solvent orthe like to obtain a paste cathode mixture slurry. Subsequently, bothsurfaces of the cathode current collector 33A are coated with thecathode mixture slurry, which is dried to form the cathode activematerial layer 33B. Thereafter, the cathode active material layer 33B iscompression-molded by using a roll pressing machine and/or the likewhile being heated as necessary. In this case, compression-molding maybe repeated several times.

Further, the anode 34 is formed by a procedure similar to that of thecathode 33 described above. An anode active material is mixed with ananode binder, an anode electric conductor, and/or the like as necessaryto prepare an anode mixture, which is subsequently dispersed in anorganic solvent or the like to form a paste anode mixture slurry.Subsequently, both surfaces of the anode current collector 34A arecoated with the anode mixture slurry, which is dried to form the anodeactive material layer 34B. Thereafter, the anode active material layer34B is compression-molded as necessary.

Further, after an electrolyte salt is dispersed in a solvent, anunsaturated cyclic ester carbonate is added thereto to prepare anelectrolytic solution.

Subsequently, a precursor solution containing an electrolytic solution,a polymer compound, and a solvent such as an organic solvent isprepared. Thereafter, the cathode 33 and the anode 34 are coated withthe precursor solution to form the gel electrolyte layer 36.Subsequently, the cathode lead 31 is attached to the cathode currentcollector 33A by using a welding method and/or the like and the anodelead 32 is attached to the anode current collector 34A by using awelding method and/or the like. Subsequently, the cathode 33 and theanode 34 provided with the electrolyte layer 36 are layered with theseparator 35 in between and are spirally wound to form the spirallywound electrode body 30. Thereafter, the protective tape 37 is adheredto the outermost periphery thereof. Subsequently, after the spirallywound electrode body 30 is sandwiched between two pieces of film-likeouter package members 40, the outer edges of the outer package members40 are bonded by a thermal fusion bonding method and/or the like toenclose the spirally wound electrode body 30 into the outer packagemembers 40. In this case, the adhesive films 41 are inserted between thecathode lead 31 and the anode lead 32, and the outer package member 40.

In the second procedure, the cathode lead 31 is attached to the cathode33, and the anode lead 32 is attached to the anode 34. Subsequently, thecathode 33 and the anode 34 are layered with the separator 35 in betweenand are spirally wound to form a spirally wound body as a precursor ofthe spirally wound electrode body 30. Thereafter, the protective tape 37is adhered to the outermost periphery thereof. Subsequently, after thespirally wound body is sandwiched between two pieces of the film-likeouter package members 40, the outermost peripheries except for one sideare bonded by using a thermal fusion bonding method and/or the like toobtain a pouched state, and the spirally wound body is contained in thepouch-like outer package member 40. Subsequently, a composition forelectrolyte containing an electrolytic solution, a monomer as a rawmaterial for the polymer compound, a polymerization initiator, and othermaterials such as a polymerization inhibitor as necessary is prepared,which is injected into the pouch-like outer package member 40.Thereafter, the outer package member 40 is hermetically sealed by usinga thermal fusion bonding method and/or the like. Subsequently, themonomer is thermally polymerized. Thereby, a polymer compound is formed,and therefore the gel electrolyte layer 36 is formed.

In the third procedure, the spirally wound body is formed and containedin the pouch-like outer package member 40 in a manner similar to that ofthe foregoing second procedure, except that the separator 35 with bothsurfaces coated with a polymer compound is used. Examples of the polymercompound with which the separator 35 is coated include a polymer (ahomopolymer, a copolymer, or a multicomponent copolymer) containingvinylidene fluoride as a component. Specific examples thereof includepolyvinylidene fluoride, a binary copolymer containing vinylidenefluoride and hexafluoro propylene as components, and a ternary copolymercontaining vinylidene fluoride, hexafluoro propylene, andchlorotrifluoroethylene as components. In addition to the polymercontaining vinylidene fluoride as a component, other one or more polymercompounds may be used. Subsequently, an electrolytic solution isprepared and injected into the outer package member 40. Thereafter, theopening of the outer package member 40 is hermetically sealed by using athermal fusion bonding method and/or the like. Subsequently, theresultant is heated while a weight is applied to the outer packagemember 40, and the separator 35 is adhered to the cathode 33 and theanode 34 with the polymer compound in between. Thereby, the polymercompound is impregnated with the electrolytic solution, and accordinglythe polymer compound is gelated to form the electrolyte layer 36.

In the third procedure, swollenness of the secondary battery issuppressed more than in the first procedure. Further, in the thirdprocedure, the monomer as a raw material of the polymer compound, thesolvent, and the like are less likely to be left in the electrolytelayer 36 compared to in the second procedure. Therefore, the formationstep of the polymer compound is favorably controlled. Therefore,sufficient adhesion characteristics are obtained between the cathode 33,the anode 34, and the separator 35, and the electrolyte layer 36.

[Function and Effect of Secondary Battery]

According to the secondary battery, the electrolyte layer 36 as a gelelectrolyte that contains the electrolytic solution and the polymercompound is included, and the electrolytic solution contains theunsaturated cyclic ester carbonate. In this case, as described above,the chemical stability of the electrolytic solution is specificallyimproved, and therefore, a decomposition reaction of the electrolyticsolution is effectively suppressed. Therefore, even if the secondarybattery is charged, discharged, or stored, the electrolytic solution isless likely to be decomposed, and accordingly superior batterycharacteristics are obtainable.

In particular, in the case where the content of the unsaturated cyclicester carbonate in the electrolytic solution is from 0.01 wt % to 10 wt% both inclusive, higher effects are obtainable. Further, in the casewhere the unsaturated cyclic ester carbonate is one of the compoundsrepresented by Formula (1-1) to Formula (1-56), in particular, is one ofthe compounds represented by Formula (2) and Formula (3), higher effectsare obtainable.

[2. Applications of Secondary Battery]

Next, a description will be given of application examples of theforegoing secondary battery.

Applications of the secondary battery are not particularly limited aslong as the secondary battery is used for a machine, a device, aninstrument, an apparatus, a system (collective entity of a plurality ofdevices and the like), or the like that is allowed to use the secondarybattery as a driving electric power source, an electric power storagesource for electric power storage, or the like. The secondary batteryused as an electric power source may be used as a main electric powersource (electric power source used preferentially), or an auxiliaryelectric power source (electric power source used instead of a mainelectric power source or used being switched from the main electricpower source). In the latter case, the main electric power source typeis not limited to the secondary battery.

Examples of applications of the secondary battery include mobileelectronic apparatuses such as a video camcoder, a digital still camera,a mobile phone, a notebook personal computer, a cordless phone, aheadphone stereo, a portable radio, a portable television, and apersonal digital assistant. Further examples thereof include a mobilelifestyle electric appliance such as an electric shaver; a memory devicesuch as a backup electric power source and a memory card; an electricpower tool such as an electric drill and an electric saw; a battery packused as an electric power source of a notebook personal computer or thelike; a medical electronic apparatus such as a pacemaker and a hearingaid; an electric vehicle such as an electric automobile (including ahybrid automobile); and an electric power storage system such as a homebattery system for storing electric power for emergency or the like. Itis needless to say that an application other than the foregoingapplications may be adopted.

Specially, the secondary battery is effectively applicable to thebattery pack, the electric vehicle, the electric power storage system,the electric power tool, the electronic apparatus, or the like. In theseapplications, since superior battery characteristics are demanded, thecharacteristics are allowed to be effectively improved by using thesecondary battery according to the embodiment of the presentapplication. It is to be noted that the battery pack is an electricpower source using a secondary battery, and is what we call an assembledbattery or the like. The electric vehicle is a vehicle that works (runs)by using a secondary battery as a driving electric power source. Asdescribed above, an automobile including a drive source other than asecondary battery (such as hybrid automobile) may be included. Theelectric power storage system is a system using a secondary battery asan electric power storage source. For example, in a home electric powerstorage system, electric power is stored in the secondary battery as anelectric power storage source, and the electric power is consumed asnecessary. Thereby, home electric products and the like become usable.The electric power tool is a tool in which a movable section (such as adrill) is moved by using a secondary battery as a driving electric powersource. The electronic apparatus is an apparatus executing variousfunctions by using a secondary battery as a driving electric powersource (electric power supply source).

A description will be specifically given of some application examples ofthe secondary battery. The configurations of the respective applicationexamples explained below are merely examples, and may be changed asappropriate.

[2-1. Battery Pack]

FIG. 3 illustrates a block configuration of a battery pack. For example,as illustrated in FIG. 3, the battery pack includes a control section61, an electric power source 62, a switch section 63, a currentmeasurement section 64, a temperature detection section 65, a voltagedetection section 66, a switch control section 67, a memory 68, atemperature detection device 69, a current detection resistance 70, acathode terminal 71, and an anode terminal 72 in a housing 60 made of aplastic material and/or the like.

The control section 61 controls operation of the whole battery pack(including a used state of the electric power source 62), and includes,for example, a central processing unit (CPU) and/or the like. Theelectric power source 62 includes one or more secondary batteries (notillustrated). The electric power source 62 is, for example, an assembledbattery including two or more secondary batteries. Connection typethereof may be a series-connected type, a parallel-connected type, or amixed type thereof. As an example, the electric power source 62 includessix secondary batteries connected in a manner of dual-parallel andthree-series.

The switch section 63 switches the used state of the electric powersource 62 (whether or not the electric power source 62 is connected toan external device) according to an instruction of the control section61. The switch section 63 includes, for example, a charge controlswitch, a discharge control switch, a charging diode, a dischargingdiode, and the like (not illustrated). The charge control switch and thedischarge control switch are, for example, semiconductor switches suchas a field-effect transistor (MOSFET) using metal oxide semiconductor.

The current measurement section 64 measures a current by using thecurrent detection resistance 70, and outputs the measurement result tothe control section 61. The temperature detection section 65 measurestemperature by using the temperature detection device 69, and outputsthe measurement result to the control section 61. The temperaturemeasurement result is used for, for example, a case in which the controlsection 61 controls charge and discharge at the time of abnormal heatgeneration or a case in which the control section 61 performs acorrection processing at the time of calculating a remaining capacity.The voltage detection section 66 measures a voltage of the secondarybattery in the electric power source 62, performs analog-to-digitalconversion (A/D conversion) on the measured voltage, and supplies theresultant to the control section 61.

The switch control section 67 controls operation of the switch section63 according to signals inputted from the current measurement section 64and the voltage measurement section 66.

The switch control section 67 executes control so that a charge currentis prevented from flowing in a current path of the electric power source62 by disconnecting the switch section 63 (charge control switch) in thecase where, for example, a battery voltage reaches an overchargedetection voltage. Thereby, in the electric power source 62, onlydischarge is allowed to be performed through the discharging diode. Itis to be noted that, for example, in the case where a large currentflows at the time of charge, the switch control section 67 blocks thecharge current.

Further, the switch control section 67 executes control so that adischarge current is prevented from flowing in the current path of theelectric power source 62 by disconnecting the switch section 63(discharge control switch) in the case where, for example, a batteryvoltage reaches an over-discharge detection voltage. Thereby, in theelectric power source 62, only charge is allowed to be performed throughthe charging diode. For example, in the case where a large current flowsat the time of discharge, the switch control section 67 blocks thedischarge current.

It is to be noted that, in the secondary battery, for example, theovercharge detection voltage is 4.2 V±0.05 V, and the over-dischargedetection voltage is 2.4 V±0.1 V.

The memory 68 is, for example, an EEPROM as a nonvolatile memory or thelike. The memory 68 stores, for example, numerical values calculated bythe control section 61 and information of the secondary battery measuredin a manufacturing step (for example, an internal resistance in theinitial state or the like). It is to be noted that, in the case wherethe memory 68 stores a full charge capacity of the secondary battery,the control section 10 is allowed to comprehend information such as aremaining capacity.

The temperature detection device 69 measures temperature of the electricpower source 62, and outputs the measurement result to the controlsection 61. The temperature detection device 69 is, for example, athermistor or the like.

The cathode terminal 71 and the anode terminal 72 are terminalsconnected to an external device (such as a notebook personal computer)driven by using the battery pack or to an external device (such as abattery charger) used for charging the battery pack. The electric powersource 62 is charged and discharged through the cathode terminal 71 andthe anode terminal 72.

[2-2. Electric Vehicle]

FIG. 4 illustrates a block configuration of a hybrid automobile as anexample of electric vehicles. For example, as illustrated in FIG. 4, theelectric vehicle includes a control section 74, an engine 75, anelectric power source 76, a driving motor 77, a differential 78, anelectric generator 79, a transmission 80, a clutch 81, inverters 82 and83, and various sensors 84 in a body 73 made of a metal. In additionthereto, the electric vehicle includes, for example, a front drive shaft85 and a front tire 86 that are connected to the differential 78 and thetransmission 80, a rear drive shaft 87, and a rear tire 88.

The electric vehicle is runnable by using one of the engine 75 and themotor 77 as a drive source. The engine 75 is a main power source, andis, for example, a petrol engine. In the case where the engine 75 isused as a power source, drive power (torque) of the engine 75 istransferred to the front tire 86 or the rear tire 88 through thedifferential 78, the transmission 80, and the clutch 81 as drivesections, for example. The torque of the engine 75 is also transferredto the electric generator 79. Due to the torque, the electric generator79 generates alternating-current electric power. The alternating-currentelectric power is converted to direct-current electric power through theinverter 83, and the converted power is stored in the electric powersource 76. Meanwhile, in the case where the motor 77 as a conversionsection is used as a power source, electric power (direct-currentelectric power) supplied from the electric power source 76 is convertedto alternating-current electric power through the inverter 82. The motor77 is driven by the alternating-current electric power. Drive power(torque) obtained by converting the electric power by the motor 77 istransferred to the front tire 86 or the rear tire 88 through thedifferential 78, the transmission 80, and the clutch 81 as the drivesections, for example.

It is to be noted that, alternatively, the following mechanism may beadopted. In the mechanism, in the case where speed of the electricvehicle is reduced by an unillustrated brake mechanism, the resistanceat the time of speed reduction is transferred to the motor 77 as torque,and the motor 77 generates alternating-current electric power by thetorque. It is preferable that the alternating-current electric power beconverted to direct-current electric power through the inverter 82, andthe direct-current regenerative electric power be stored in the electricpower source 76.

The control section 74 controls operation of the whole electric vehicle,and, for example, includes a CPU and/or the like. The electric powersource 76 includes one or more secondary batteries (not illustrated).Alternatively, the electric power source 76 may be connected to anexternal electric power source, and electric power may be stored byreceiving the electric power from the external electric power source.The various sensors 84 are used, for example, for controlling the numberof revolutions of the engine 75 or for controlling opening level of anunillustrated throttle valve (throttle opening level). The varioussensors 84 include, for example, a speed sensor, an acceleration sensor,an engine frequency sensor, and/or the like.

The description has been hereinbefore given of the hybrid automobile asan electric vehicle. However, examples of the electric vehicles mayinclude a vehicle (electric automobile) working by using only theelectric power source 76 and the motor 77 without using the engine 75.

[2-3. Electric Power Storage System]

FIG. 5 illustrates a block configuration of an electric power storagesystem. For example, as illustrated in FIG. 5, the electric powerstorage system includes a control section 90, an electric power source91, a smart meter 92, and a power hub 93 inside a house 89 such as ageneral residence and a commercial building.

In this case, the electric power source 91 is connected to, for example,an electric device 94 arranged inside the house 89, and is connectableto an electric vehicle 96 parked outside the house 89. Further, forexample, the electric power source 91 is connected to a private powergenerator 95 arranged inside the house 89 through the power hub 93, andis connectable to an external concentrating electric power system 97thorough the smart meter 92 and the power hub 93.

It is to be noted that the electric device 94 includes, for example, oneor more home electric appliances such as a refrigerator, an airconditioner, a television, and a water heater. The private powergenerator 95 is, for example, one or more of a solar power generator, awind-power generator, and the like. The electric vehicle 96 is, forexample, one or more of an electric automobile, an electric motorcycle,a hybrid automobile, and the like. The concentrating electric powersystem 97 is, for example, one or more of a thermal power plant, anatomic power plant, a hydraulic power plant, a wind-power plant, and thelike.

The control section 90 controls operation of the whole electric powerstorage system (including a used state of the electric power source 91),and, for example, includes a CPU and/or the like. The electric powersource 91 includes one or more secondary batteries (not illustrated).The smart meter 92 is, for example, an electric power meter compatiblewith a network arranged in the house 89 demanding electric power, and iscommunicable with an electric power supplier. Accordingly, for example,while the smart meter 92 communicates with external as necessary, thesmart meter 92 controls the balance between supply and demand in thehouse 89 and allows effective and stable energy supply.

In the electric power storage system, for example, electric power isstored in the electric power source 91 from the concentrating electricpower system 97 as an external electric power source through the smartmeter 92 and the power hub 93, and electric power is stored in theelectric power source 91 from the private power generator 95 as anindependent electric power source through the power hub 93. Asnecessary, the electric power stored in the electric power source 91 issupplied to the electric device 94 or the electric vehicle 96 accordingto an instruction of the control section 90. Therefore, the electricdevice 94 becomes operable, and the electric vehicle 96 becomeschargeable. That is, the electric power storage system is a systemcapable of storing and supplying electric power in the house 89 by usingthe electric power source 91.

The electric power stored in the electric power source 91 is arbitrarilyusable. Therefore, for example, electric power is allowed to be storedin the electric power source 91 from the concentrating electric powersystem 97 in the middle of the night when an electric rate isinexpensive, and the electric power stored in the electric power source91 is allowed to be used during daytime hours when an electric rate isexpensive.

It is to be noted that the foregoing electric power storage system maybe arranged for each household (family unit), or may be arranged for aplurality of households (family units).

[2-4. Electric Power Tool]

FIG. 6 illustrates a block configuration of an electric power tool. Forexample, as illustrated in FIG. 6, the electric power tool is anelectric drill, and includes a control section 99 and an electric powersource 100 in a tool body 98 made of a plastic material and/or the like.For example, a drill section 101 as a movable section is attached to thetool body 98 in an operable (rotatable) manner.

The control section 99 controls operation of the whole electric powertool (including a used state of the electric power source 100), andincludes, for example, a CPU and/or the like. The electric power source100 includes one or more secondary batteries (not illustrated). Thecontrol section 99 executes control so that electric power is suppliedfrom the electric power source 100 to the drill section 101 as necessaryaccording to operation of an unillustrated operation switch to operatethe drill section 101.

EXAMPLES

Specific Examples according to the embodiment of the present applicationwill be described in detail.

Examples 1-1 to 1-14

The laminated film type lithium ion secondary battery illustrated inFIG. 1 and FIG. 2 was fabricated by the following procedure.

In fabricating the cathode 33, first, lithium carbonate (Li₂CO₃) andcobalt carbonate (CoCO₃) were mixed at a molar ratio ofLi₂CO₃:CoCO₃=0.5:1. Subsequently, the mixture was fired in the air (at900° C. for 5 hours). Thereby, lithium-cobalt composite oxide (LiCoO₂)was obtained. Subsequently, 91 parts by mass of a cathode activematerial (LiCoO₂), 6 parts by mass of a cathode electric conductor(graphite), and 3 parts by mass of a cathode binder (polyvinylidenefluoride: PVDF) were mixed to obtain a cathode mixture. Subsequently,the cathode mixture was dispersed in N-methyl-2-pyrrolidone (NMP) toobtain a paste cathode mixture slurry. Subsequently, both surfaces ofthe cathode current collector 33A in the shape of a strip (Al foil being20 μm thick) were coated with the cathode mixture slurry uniformly byusing a coating device, which was dried to form the cathode activematerial layer 33B. Finally, the cathode active material layer 33B wascompression-molded by using a roll pressing machine. In forming thecathode 33, the thickness of the cathode active material layer 33B wasadjusted so that lithium metal was not precipitated on the anode 34 atthe time of full charge.

In fabricating the anode 34, first, 90 parts by mass of an anode activematerial (artificial graphite) and 10 parts by mass of an anode binder(PVDF) were mixed to obtain an anode mixture. Subsequently, the anodemixture was dispersed in NMP to obtain paste anode mixture slurry.Subsequently, both surfaces of the anode current collector 34A in theshape of a strip (electrolytic Cu foil being 15 μm thick) were coatedwith the anode mixture slurry uniformly by using a coating device, whichwas dried to form the anode active material layer 34B. Finally, theanode active material layer 34B was compression-molded by using a rollpressing machine.

In preparing an electrolytic solution, an electrolyte salt (LiPF₆) wasdissolved in a solvent (ethylene carbonate (EC) and ethyl methylcarbonate (EMC)). In this case, the mixture ratio (weight ratio) of thesolvent was EC:EMC=50:50, and the content of the electrolyte salt withrespect to the solvent was 1 mol/kg.

In assembling the secondary battery, first, the cathode lead 31 made ofAl was welded to one end of the cathode current collector 33A, and theanode lead 32 made of Ni was welded to one end of the anode currentcollector 34A. Subsequently, the cathode 33, the separator 35, the anode34, and the separator 35 were layered in this order and were spirallywound in the longitudinal direction. After that, the winding end portionwas fixed by using the protective tape 37 made of an adhesive tape toform a spirally wound body as a precursor of the spirally woundelectrode body 30. In the separator 35, a polymer compound (PVDF) wasformed on both surfaces of a base material layer. The base materiallayer had a three-layer structure (thickness: 23 μm) in which a filmmade of porous polyethylene as a main component was sandwiched betweenfilms made of porous polypropylene as a main component. Subsequently,the spirally wound body was sandwiched between the outer package members40. After that, the outermost peripheries except for one side werethermally bonded, and the spirally wound body was contained in thepouch-like outer package member 40. The outer package member 40 was alaminated film (total thickness: 100 μm) having a three-layer structurein which a nylon film (thickness: 30 μm), an Al foil (thickness: 40 μm),and a non-stretched polypropylene film (thickness: 30 μm) were layeredin this order from the outside. Subsequently, an electrolytic solutionwas injected through an opening of the outer package member 40, thepolymer compound layer was impregnated with the electrolytic solution,and thereby the electrolyte layer 36 as a gel electrolyte was formed.Accordingly, the cathode 33 and the anode 34 were layered with theseparator 35 and the electrolyte layer 36 in between and were spirallywound, and therefore the spirally wound electrode body 30 was formed.Thereby, the laminated film type secondary battery was completed.

In fabricating the secondary batteries, for comparison, instead of thegel electrolyte (electrolyte layer 36), a liquid electrolyte(electrolytic solution) was used as it is, and the separator 35 wasimpregnated with the electrolytic solution.

Battery characteristics (cycle characteristics and load characteristics)of the secondary battery were examined. Results illustrated in Table 1were obtained.

In examining the cycle characteristics, one cycle of charge anddischarge was performed on the secondary battery in the ambienttemperature environment (23° C.) to stabilize the battery state. Afterthat, another one cycle of charge and discharge was performed on thesecondary battery in the same environment, and a discharge capacity wasmeasured. Subsequently, the secondary battery was repeatedly charged anddischarged until the total number of cycles reached 100 in thehigh-temperature environment (40° C.), and a discharge capacity wasmeasured. From these results, cycle retention ratio (%)=(dischargecapacity at the 100th cycle/discharge capacity at the second cycle)×100was calculated. At the time of charge, charge was performed at a currentof 0.2 C until the voltage reached the upper limit voltage of 4.2 V, andfurther charge was performed at a constant voltage until the currentreached 0.05 C. At the time of discharge, constant current discharge wasperformed at a current of 0.2 C until the voltage reached the finalvoltage of 2.5 V. “0.2 C” and “0.05 C” are current values at which thebattery capacity (theoretical capacity) is fully discharged in 5 hoursand 20 hours, respectively.

In examining the load characteristics, a secondary battery with itsbattery state stabilized by a procedure similar to that in the case ofexamining the cycle characteristics was used. One cycle of charge anddischarge was performed on the secondary battery in the ambienttemperature environment (23° C.), and a discharge capacity was measured.Subsequently, the secondary battery was repeatedly charged anddischarged until the total number of cycles reached 100 in alow-temperature environment (−10° C.), and a discharge capacity wasmeasured. From these results, load retention ratio (%)=(dischargecapacity at the 100th cycle/discharge capacity at the second cycle)×100was calculated. The charge conditions were similar to those in the caseof examining the high-temperature cycle characteristics. At the time ofdischarge, constant current discharge was performed at a current of 1 Cuntil the voltage reached the final voltage of 2.5 V. “1 C” is a currentvalue at which the battery capacity is fully discharged in 1 hour.

TABLE 1 Unsaturated cyclic ester carbonate Cycle Load PolymerElectrolyte Content retention retention Example State compound saltSolvent Type (wt %) ratio (%) ratio (%) 1-1 Gel PVDF LiPF₆ EC + EMCFormula (1-1) 0.01 61 71 1-2 0.1 65 73 1-3 0.5 68 76 1-4 1 75 80 1-5 280 78 1-6 5 79 73 1-7 10 60 70 1-8 Formula (1-4) 2 78 73 1-9 Formula(1-16) 2 76 75 1-10 Formula (1-18) 2 77 74 1-11 Formula (1-32) 2 78 751-12 — — 58 70 1-13 Liquid — LiPF₆ EC + EMC — — 20 85 1-14 Formula (1-1)2 18 85

In the case where the liquid electrolyte (electrolytic solution) wasused, the load retention ratios were retained while the cycle retentionratios were decreased according to presence of the unsaturated cyclicester carbonate in the electrolytic solution. Meanwhile, in the casewhere the gel electrolyte (electrolyte layer 36) was used, both thecycle retention ratios and the load retention ratios were improvedaccording to presence of the unsaturated cyclic ester carbonate. Theforegoing results show the following. The function of the unsaturatedcyclic ester carbonate with respect to the cycle retention ratio and theload retention ratio is a specific and advantageous function. That is,such a function is not obtained in the case where a liquid electrolyteis used, but is obtained in the case where a gel electrolyte is used.

In particular, in the case where the unsaturated cyclic ester carbonatewas used, if the content thereof was from 0.01 wt % to 10 wt % bothinclusive, and more specifically from 0.1 wt % to 5 wt % both inclusive,higher cycle retention ratios and higher load retention ratios wereobtained.

Examples 2-1 to 2-7

Secondary batteries were fabricated by a procedure similar to that ofExample 1-5, except that the composition of the solvent was changed asillustrated in Table 2, and the respective characteristics wereexamined. In this case, the following solvents were newly used. That is,vinylene carbonate (VC) as other unsaturated cyclic ester carbonate,4-fluoro-1,3-dioxolane-2-one (FEC),trans-4,5-difluoro-1,3-dioxolane-2-one (t-DFEC), andbis(fluoromethyl)carbonate (DFDMC) as halogenated ester carbonates,propene sultone (PRS) as sultone, succinic anhydride (SCAH) andsulfopropionic anhydride (PSAH) as acid anhydrides were used. Thecontent of VC in the solvent was 2 wt %, the content of FEC, t-DFEC, orDFDMC in the solvent was 5 wt %, and the content of PRS, SCAH, or PSAHin the solvent was 1 wt %.

TABLE 2 Unsaturated cyclic ester carbonate Cycle Load PolymerElectrolyte Content retention retention Example State compound saltSolvent Type (wt %) ratio (%) ratio (%) 2-1 Gel PVDF LiPF₆ EC + EMC VCFormula (1-1) 2 90 78 2-2 FEC 88 78 2-3 t-DFEC 85 78 2-4 DFDMC 86 78 2-5PRS 90 82 2-6 SCAH 90 75 2-7 PSAH 92 85

Even if the composition of the solvent was changed, a high cycleretention ratio and a high load retention ratio were obtained. Inparticular, in the case where the electrolytic solution contained otherunsaturated cyclic ester carbonate, the halogenated ester carbonate, thesultone, or the acid anhydride, one or both of the cycle retention ratioand the load retention ratio were more increased.

Examples 3-1 to 3-3

Secondary batteries were fabricated by a procedure similar to that ofExample 1-5 except that the composition of the electrolyte salt waschanged as illustrated in Table 3, and the respective characteristicswere examined. As an electrolyte salt combined with LiPF₆, lithiumtetrafluoroborate (LiBF₄), bis [oxalato-O,O′] lithium borate (LiBOB)represented by Formula (8-6), or bis(trifluoromethanesulfonyl)imidelithium (LiN(CF₃SO₂)₂: LiTFSI) was used. In this case, the content ofLiPF₆ was 0.9 mol/kg with respect to the solvent, and the content ofLiBF₄ or the like was 0.1 mol/kg with respect to the solvent.

TABLE 3 Unsaturated cyclic ester carbonate Cycle Load PolymerElectrolyte Content retention retention Example State compound saltSolvent Type (wt %) ratio (%) ratio (%) 3-1 Gel PVDF LiPF₆ LiBF₄ EC +EMC Formula (1-1) 2 85 78 3-2 LiBOB 88 75 3-3 LiTFSI 88 80

Even if the composition of the electrolyte salt was changed, a highcycle retention ratio and a high load retention ratio were obtained. Inparticular, in the case where the electrolytic solution contained otherelectrolyte salt such as LiBF₄, the cycle retention ratio and the loadretention ratio were more increased.

The present application has been described with reference to theembodiment and Examples. However, the present application is not limitedto the examples described in the embodiment and Examples, and variousmodifications may be made. For example, the description has been givenof the lithium ion secondary battery as a secondary battery type.However, applicable secondary battery type is not limited thereto. Thesecondary battery of the present application is similarly applicable toa secondary battery in which the anode capacity includes a capacity byinserting and extracting lithium ions and a capacity associated withprecipitation and dissolution of lithium metal, and the battery capacityis expressed by the sum of these capacities. In this case, an anodematerial capable of inserting and extracting lithium ions is used as ananode active material, and the chargeable capacity of the anode materialis set to a smaller value than the discharge capacity of the cathode.

Further, the description has been given with the specific example of thecase in which the battery structure is the laminated film type, and thebattery device has the spirally wound structure. However, applicablestructures are not limited thereto. The secondary battery of the presentapplication is similarly applicable to a battery having other batterystructure such as a cylindrical type battery, a square type battery, acoin type battery, and a button type battery or a battery in which thebattery device has other structure such as a laminated structure.

Further, the description has been given of the case using Li as anelectrode reactant. However, the electrode reactant is not necessarilylimited thereto. As an electrode reactant, for example, other Group 1element such as Na and K, a Group 2 element such as Mg and Ca, or otherlight metals such as Al may be used. The effect of the presentapplication may be obtained without depending on the electrode reactanttype, and therefore, even if the electrode reactant type is changed, asimilar effect is obtainable.

Further, with regard to the content of the unsaturated cyclic estercarbonate, the description has been given of the appropriate rangederived from the results of Examples. However, the description does nottotally deny a possibility that the content is out of the foregoingrange. That is, the foregoing appropriate range is the rangeparticularly preferable for obtaining the effects of the presentapplication. Therefore, as long as the effects of the presentapplication are obtained, the content may be out of the foregoing rangein some degrees.

It is possible to achieve at least the following configurations from theabove-described exemplary embodiment and the modifications of thedisclosure.

(1) A secondary battery including:

a cathode;

an anode; and

a gel electrolyte, wherein

the gel electrolyte includes an electrolytic solution and a polymercompound, and

the electrolytic solution includes an unsaturated cyclic ester carbonaterepresented by the following Formula (1),

where X is a divalent group in which m number of >C═CR1-R2 and n numberof >CR3R4 are bonded in any order; each of R1 to R4 is one of a hydrogengroup, a halogen group, a monovalent hydrocarbon group, a monovalenthalogenated hydrocarbon group, a monovalent oxygen-containinghydrocarbon group, and a monovalent halogenated oxygen-containinghydrocarbon group; any two or more of the R1 to the R4 are allowed to bebonded to one another; and m and n satisfy m≥1 and n≥0.(2) The secondary battery according to (1), wherein

the halogen group is one of a fluorine group, a chlorine group, abromine group, and an iodine group, and

the monovalent hydrocarbon group, the monovalent halogenated hydrocarbongroup, the monovalent oxygen-containing hydrocarbon group, and themonovalent halogenated oxygen-containing hydrocarbon group include analkyl group with carbon number from 1 to 12 both inclusive, an alkenylgroup with carbon number from 2 to 12 both inclusive, an alkynyl groupwith carbon number from 2 to 12 both inclusive, an aryl group withcarbon number from 6 to 18 both inclusive, a cycloalkyl group withcarbon number from 3 to 18 both inclusive, an alkoxy group with carbonnumber from 1 to 12 both inclusive, a group obtained by bonding two ormore thereof, and a group obtained by substituting each of part or allof hydrogen groups thereof by a halogen group.

(3) The secondary battery according to (1) or (2), wherein theunsaturated cyclic ester carbonate is represented by one of thefollowing Formula (2) and Formula (3),

where each of R5 to R10 is one of a hydrogen group, a halogen group, amonovalent hydrocarbon group, a monovalent halogenated hydrocarbongroup, a monovalent oxygen-containing hydrocarbon group, and amonovalent halogenated oxygen-containing hydrocarbon group; the R5 andthe R6 may be bonded to each other; and any two or more of the R7 to theR10 may be bonded to one another.(4) The secondary battery according to any one of (1) to (3), whereinthe unsaturated cyclic ester carbonate is represented by one of thefollowing Formula (1-1) to Formula (1-56),

(5) The secondary battery according to any one of (1) to (4), wherein acontent of the unsaturated cyclic ester carbonate in the electrolyticsolution is from about 0.01 weight percent to about 10 weight percentboth inclusive.(6) The secondary battery according to any one of (1) to (5), whereinthe secondary battery is a lithium ion secondary battery.(7) A battery pack including:

the secondary battery according to any one of (1) to (6);

a control section controlling a used state of the secondary battery; and

a switch section switching the used state of the secondary batteryaccording to an instruction of the control section.

(8) An electric vehicle including:

the secondary battery according to any one of (1) to (6);

a conversion section converting electric power supplied from thesecondary battery into drive power;

a drive section operating according to the drive power; and

a control section controlling a used state of the secondary battery.

(9) An electric power storage system including:

the secondary battery according to any one of (1) to (6);

one or more electric devices supplied with electric power from thesecondary battery; and

a control section controlling the supplying of the electric power fromthe secondary battery to the one or more electric devices.

(10) An electric power tool including:

the secondary battery according to any one of (1) to (6); and

a movable section being supplied with electric power from the secondarybattery.

(11) An electronic apparatus including

the secondary battery according to any one of (1) to (6) as an electricpower supply source.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope of the present subjectmatter and without diminishing its intended advantages. It is thereforeintended that such changes and modifications be covered by the appendedclaims.

The invention is claimed as follows:
 1. A secondary battery comprising:a cathode; an anode; and a gel electrolyte, wherein the gel electrolyteincludes an electrolytic solution and a polymer, and the electrolyticsolution includes 0.1 to 5 wt % of an unsaturated cyclic ester carbonaterepresented by Formula (2):

wherein R5 and R6 are one of a halogen group, a monovalent halogenatedhydrocarbon group, a monovalent oxygen-containing hydrocarbon group, anda monovalent halogenated oxygen-containing hydrocarbon group; and whereR5 and R6 may be bonded to each other.
 2. The secondary batteryaccording to claim 1, wherein the electrolytic solution comprises anelectrolyte salt comprising LiPF₆ dissolved in a solvent comprisingethylene carbonate (EC) and ethyl methyl carbonate (EMC).
 3. Thesecondary battery according to claim 2, wherein a weight ratio of thesolvent is EC:EMC=50:50.
 4. The secondary battery according to claim 2,wherein a content of the electrolyte salt with respect to the solvent is1 mol/kg.
 5. The secondary battery according to claim 1, wherein thepolymer is selected from the group consisting of polyvinylidene fluorideand a copolymer of vinylidene fluoride and hexafluoro propylene.
 6. Thesecondary battery according to claim 5, wherein the polymer ispolyvinylidene fluoride.
 7. The secondary battery according to claim 1,wherein the electrolytic solution consists of the unsaturated cyclicester carbonate and one or more of ethylene carbonate, propylenecarbonate, dimethyl carbonate, diethyl carbonate, and ethyl methylcarbonate.
 8. A battery pack comprising: the secondary battery accordingto claim 1; and a control section controlling a used state of thesecondary battery.
 9. An electric vehicle comprising: the secondarybattery according to claim 1; a conversion section converting electricpower supplied from the secondary battery into drive power; a drivesection operating according to the drive power; and a control sectioncontrolling a used state of the secondary battery.
 10. An electric powerstorage system comprising: the secondary battery according to claim 1;one or more electric devices supplied with electric power from thesecondary battery; and a control section controlling supplying of theelectric power from the secondary battery to the one or more electricdevices.
 11. An electric power tool comprising: the secondary batteryaccording to claim 1; and a moveable section being supplied withelectric power from the secondary battery.
 12. An electronic apparatuscomprising: an electric power supply source including the secondarybattery according to claim 1.